1. Field of the Invention
The field of this invention resides in the area of adjustable valve box adapters to raise or lower a valve box cover when needed.
2. History of the Prior Art
When the level of a street changes, for example by the addition of more pavement or by the settling of the roadbed, it is usually necessary to completely dig up the entire valve box frame to reinstall them at the new grade level. This procedure is costly and causes traffic delays. Also if a valve box is broken such as by its rim having been struck by a snow plow or the like, one would have to dig it out of the ground and replace it. In order to avoid the digging out of such valve boxes, several different types of adapters have been utilized to raise or lower the valve box cover to the new grade of the roadway. One such type is called a fixed adapter which is available in various heights such as 1" or 2", etc. and which rests on the top rim of the existing in-street valve box. Many times though the top rim can be worn, damaged or uneven which condition may eventually cause such adapters to shift and become dislodged. Another type of adapter is the slip or slide adapter which has skirts of various lengths that slide into the valve box barrel section to adjust to various heights. Such adapters are limited to a minimum raising height of 2" or 3" because its cover support section being the diameter of the valve box rim extends above it and is thicker than the standard thickness of the pavement. Adjustable frames have also been made which include screw adjustment means to lower an inner frame within an outer frame, but these units usually have complex structures which may become impacted with material and fail after a period of time under heavy use. These adapters are also susceptible to frost forming in the threads which often have as much as 1" of play and which ice formation can cause damage to the adapters due to expansion therein.